<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><span>Mikael,</span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><span><br></span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><span>When I add the +no_uoff parameter, I get different numbers for Ann Arbor Michigan:</span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><span><br></span></div><div><span>-9992196.95 22682402.40<br></span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><span><br></span></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">They are also out of bounds -- all 4 bounding box numbers have 6 figures to the left of the decimal point. I am assuming that the
Michigan shapefile is OK. The difference between the bounding box limits is approximately 600-700 km, which seems correct (I measured a road atlas using a long ruler).</div><div><br></div><div>The figures I got using the no_uoff parameter are more than 6 figures to the left of the decimal point.</div><div><br></div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; ">The gamma parameter makes no difference with the no_uoff parameter. The gamma parameter without the no_uoff parameter gives different numbers for Ann Arbor:</div><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; "><br></div><div>-7945305.71 17799792.28<br></div><div><br></div><div>Still out of bounds.</div><div><br></div><div>I have proj Rel. 4.7.1, 23 September 2009 (came with ubuntu Linux 12.04).</div><div><br></div><div>Am I making some mistake, or does proj.4 not work with Hotine Oblique
Mercator?</div><div><br></div><div>Thanks,<br></div><div><br></div><div>Rick</div><div><br></div> <div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "> <div style="font-size: 12pt; font-family: 'times new roman', 'new york', times, serif; "> <div dir="ltr"> <font size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Mikael Rittri <Mikael.Rittri@carmenta.com><br> <b><span style="font-weight: bold;">To:</span></b> Rick Graves <gravesricharde@yahoo.com>; PROJ.4 and generalProjections Discussions <proj@lists.maptools.org> <br><b><span style="font-weight: bold;">Cc:</span></b> "proj@lists.maptools.org" <proj@lists.maptools.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Sunday, July 22, 2012 12:21 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [Proj] does proj.4 work with Hotine Oblique Mercator?<br> </font> </div> <br>
<div id="yiv1227990762">
<div><div>Hello Rick.</div><div>You need to add </div><div><br></div><div> +no_uoff</div><div><br></div><div>to your Proj.4 definition. This is just a flag, so it doesn't need any numerical value.</div><div>But it must be included so that you get what EPSG calls "Hotine Oblique Mercator Variant A".</div><div>Without it, you get the Variant B instead. One could say that the Hotine Oblique Mercator class has two</div><div>distinct construction methods (for historical reasons), and the GIS community hasn't been able</div><div>to agree <span class="yiv1227990762Apple-style-span" style="">to use only one. </span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">The names Variant A and B are fairly recent EPSG names. In WKT etc., other names for the </span></div><div><span class="yiv1227990762Apple-style-span" style="">variants appear
(usually different for different WKT dialects).</span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">See also <a rel="nofollow" target="_blank" href="http://trac.osgeo.org/proj/ticket/104">http://trac.osgeo.org/proj/ticket/104</a></span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">(Possibly, with Proj 4.8.0 you should also add</span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style=""> +gamma=337.25556</span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">for the rectified grid angle, but I think an omitted gamma defaults to the given alpha value,</span></div><div><span
class="yiv1227990762Apple-style-span" style="">so an explicit gamma is probably unnecessary in your case.)</span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">Best regards,</span></div><div><span class="yiv1227990762Apple-style-span" style=""><br></span></div><div><span class="yiv1227990762Apple-style-span" style="">Mikael Rittri</span></div><div><span class="yiv1227990762Apple-style-span" style="">Carmenta</span></div><div><span class="yiv1227990762Apple-style-span" style="">Sweden</span></div><div><span class="yiv1227990762Apple-style-span" style="">http://www.carmenta.com</span></div><div><br>22 jul 2012 kl. 18:42 skrev "Rick Graves" <<a rel="nofollow" ymailto="mailto:gravesricharde@yahoo.com" target="_blank" href="mailto:gravesricharde@yahoo.com">gravesricharde@yahoo.com</a>>:<br><br></div><blockquote type="cite"><div><div style="color: rgb(0, 0, 0);
background-color: rgb(255, 255, 255); font-size: 12pt; font-family: arial, helvetica, sans-serif; "><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; ">Hey,</div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "><br></div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; ">I am not sure that proj.4 is converting latitude and longitude into Hotine Oblique Mercator <span style="font-size:12pt;">coordinates correctly. (But I am a newbie at cartography and such, so please bear with me, I could be making a mistake.)</span></div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "><br></div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; ">As a result of the 2010 census in the USA, many states have redrawn their congressional districts. Michigan is one, and the shapefiles for their new districts were created
using the Hotine Oblique Mercator projection to get the whole state onto one map with a minimum of overall distortion. There is a map and explanation here:</div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "><br></div><div><font face="arial, helvetica, sans-serif">http://www.michigan.gov/documents/DNR_Map_Proj_and_MI_Georef_Info_20889_7.pdf</font><br></div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "><br></div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; ">One can download Michigan's new Congressional district shapefiles from here:</div><div style="font-size: 12pt; font-family: arial, helvetica, sans-serif; "><br></div><div><font face="arial, helvetica, sans-serif">http://www.mcgi.state.mi.us/mgdl/?rel=thext&action=thmname&cid=9&cat=Legislative+Districts+2010+US+Congress</font><br></div><div><font face="arial, helvetica,
sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif">The included prj file has this info:</font></div><div><font face="arial, helvetica, sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif"><div>PROJCS["NAD83 / Michigan Oblique Mercator",</div><div>GEOGCS["NAD83",</div><div> DATUM["North_American_Datum_1983",</div><div><span class="yiv1227990762Apple-tab-span" style="white-space:pre;"> </span>SPHEROID["GRS 1980",6378137,298.257222101,</div><div><span class="yiv1227990762Apple-tab-span" style="white-space:pre;"> </span> AUTHORITY["EPSG","7019"]],</div><div><span class="yiv1227990762Apple-tab-span" style="white-space:pre;"> </span>AUTHORITY["EPSG","6269"]],</div><div> PRIMEM["Greenwich",0,</div><div><span class="yiv1227990762Apple-tab-span" style="white-space:pre;"> </span>AUTHORITY["EPSG","8901"]],</div><div>
UNIT["degree",0.01745329251994328,</div><div><span class="yiv1227990762Apple-tab-span" style="white-space:pre;">
</span>AUTHORITY["EPSG","9122"]],</div><div> AUTHORITY["EPSG","4269"]],</div><div>UNIT["metre",1,</div><div> AUTHORITY["EPSG","9001"]],</div><div>PROJECTION["Hotine_Oblique_Mercator"],</div><div>PARAMETER["latitude_of_center",45.30916666666666],</div><div>PARAMETER["longitude_of_center",-86],</div><div>PARAMETER["azimuth",337.25556],</div><div>PARAMETER["rectified_grid_angle",337.25556],</div><div>PARAMETER["scale_factor",0.9996],</div><div>PARAMETER["false_easting",2546731.496],</div><div>PARAMETER["false_northing",-4354009.816],</div><div>AUTHORITY["EPSG","3078"],</div><div>AXIS["X",EAST],</div><div>AXIS["Y",NORTH]]</div><div><br></div><div>This page has info on the <span style="font-size:16px;">Hotine Oblique Mercator:</span></div><div><span style="font-size:16px;"><br></span></div><div>http://www.remotesensing.org/geotiff/proj_list/hotine_oblique_mercator.html<br></div><div><br></div><div>Using that, I came up with
this command to invoke proj:</div><div><br></div><div><div>proj +proj=omerc +lat_0=45.30916666666666 +lonc=-86 +alpha=337.25556 +k_0=0.9996 +x_0=2546731.496 +y_0=-4354009.816</div><div><br></div><div>I get a latitude and longitude for Ann Arbor Michigan of 42 15 N - 83 45 W here:</div><div><br></div><div>http://wiki.answers.com/Q/What_is_the_latitude_and_longitude_of_ann_arbor_mi<br></div><div><br></div><div>Plugging 42d15N 83d45W into proj, I get -7945305.71 17799792.28. But the bounding box of the entire state's shape file is this:</div><div><br></div><div>161318.17712499946, 128066.04250000045, 791832.2827499993, 859206.8181249984<br></div><div><br></div><div>The values I get from proj are both out of bounds. </div><div><br></div><div>Am I doing something wrong?</div><div><br></div><div>Thanks,</div><div><br></div><div>Rick Graves</div><div><br></div></div></font></div></div></div></blockquote><blockquote
type="cite"><div><span>_______________________________________________</span><br><span>Proj mailing list</span><br><span><a rel="nofollow" ymailto="mailto:Proj@lists.maptools.org" target="_blank" href="mailto:Proj@lists.maptools.org">Proj@lists.maptools.org</a></span><br><span>http://lists.maptools.org/mailman/listinfo/proj</span></div></blockquote></div></div><br><br> </div> </div> </div></body></html>